Recently, identification cards such as a cash card, an employee identification card, a member card, a student identification card, a foreigner registration certificate card and a driver's license card have become wide spread. An IC module is built-into the identification card. The card is generally prepared by, for example, a method in which an inlet having a circuit base plate having thereon an IC chip and an antenna is inserted between two sheets of Polyethylene terephthalate (PET) film, and the sheets are pasted together by a moisture-hardening type adhesive agent, UV-hardening type adhesive agent or a two-part liquid mixture type adhesive agent, and then punched into a shape of the card.
It is required that the pasting by the adhesive agent is carried out under a relatively high temperature from the viewpoint of the conveyance suitability of a card substrate due to a shrinkage and bending of the support (referred to as a sheet material in the present invention). Accordingly, moisture-hardening adhesive agents are preferably used among the adhesive agents capable of adhering at low temperature.
However, the majority of the moisture-hardening type adhesive agents require a relatively long period for complete hardening.
The reaction can be accelerated by putting the pasted sheets into a high temperature and high moisture environment resulting in a shortening of the hardening time. However, a problem of the formation of a bulge in the card, caused by the generation of carbon dioxide gas, may result.
Further, the pasted sheets are frequently stored in a stacked state, which preserves space over arranging the sheets all in one plane.
A problem of sheet deformity is raised when the sheets are stacked since the surface of the sheets have irregularities caused by the presence of the IC chip in the sheet.
Furthermore, the reaction speed is slowed since moisture can have difficultly entering into the pasted sheets when the sheets are stacked. Besides, in cases where pasted sheets are cut into a card shape, the adhesive agents, which become hard and hardly extendable after hardening, are preferable since cards having a smooth cut portion can be obtained. The adhesive agent having a low rupture extensibility is very easily handled.
However, in such cases, the card tends to be breakable in normal use since the whole card is made hard. Accordingly, the card is easily broken when the card is put into the back pocket of trousers worn by a man and the man changes his posture since a high stress is loaded to the card under this condition. On the other hand, when an adhesive agent having a large rupture extensibility after hardening is used, the sheet become softer, however the sheet is difficult to punch into the card shape resulting in a lower production efficiency. Additionally scraps of the extended adhesive agent adhere to the edges of the card, preventing the card from conveying properly in the to the next printing process and the lamination process, for example, resulting in problems for the manufacturing process. An improvement to the process is therefore desired.